The proposed studies are to determine at what point in the process of transcription, nuclear-to-cytoplasmic transport, and translation a qualitative difference emerges between heterogeneous RNA (H-RNA) sequences of normal and malignant cells and to assess its relevance to malignant transformation. Preliminary studies suggested that for reiterated sequences, the first changes are beyond the level of transcription. In the proposed studies, two slow growing hepatomas with normal karyotype and chromosome number, hyperplastic (preneoplastic) liver nodules,non-neoplastic but rapidly dividing neonatal or regenerating liver cells will be fractionated into nuclei, microsomes or free and bound polysomes and a post microsomal particulate fraction. Differences in unique sequences will be assayed by saturation of unique DNA sequences with combinations of I125-labelled RNA from control and and neoplastic tissues. Differences in reiterated sequences will be checked by standard competitive hybridization studies.